1. Field of the Invention
The present invention relates to a device for determining the disintegration time of compressed pharmaceutical mold bodies, such as tablets and capsules, comprising a frame which can be lowered into a vessel filled with a liquid, having a center column and a floor including a plurality of bore holes, wherein the bore holes are covered from below with a sieve and wherein test tubes in upright position are disposed within the frame, wherein in each case a disk with holes passing through the disk in the direction of the center axis can be movably brought in into the test tube as a weight onto individual pharmaceutical mold bodies, wherein a permanent magnet is disposed at the lower side of the disk directed toward the floor, wherein in each case a magnetic field sensor element is disposed below the grid of the floor, as well as a method for this purpose.
2. Brief Description of the Background of the Invention Including Prior Art
The disintegration time measurement of compressed pharmaceutical mold bodies, such as tablets and capsules, is performed according to a standardized test arrangement in order to assure the reproducibility of the measurement results, in particular according to Deutsches Arzneibuch, DAB 10, 3. Supplement 1994 or Europaeisches Arzneibuch or USP (USA). It is determined by the disintegration test, if the tablets or capsules disintegrate in a liquid medium within the pre-scribed time under precisely performed conditions. The main part of the apparatus comprises a rigid frame, which contains six cylindrical test tubes made of glass. Each test tube is furnished with a cylindrical disk made of a transparent plastic material of a precisely pre-scribed relative density and size, which exhibits 5 bore holes passing through, wherein one of the bore holes is led through the center axis of the disk. The test tubes are supported in a vertical position by an upper transparent plate made of plastic material and by a lower transparent plate made of plastic material, wherein the transparent plates in each case have six bore holes. All bore holes have the same distance from the center point and the same distance from each other. A sieve made of stainless steel wire is disposed at the bottom side of the lower plate. A metal column is disposed in the middle of the plates such that the apparatus can be hanged at the metal column in a hanging device and can be moved upward and downward by way of a motor uniformly 28 to 32 times each minute over 50 to 60 mm. For this purpose the apparatus is hanged in a suitable vessel, wherein the vessel contains the pre-scribed liquid. After the filling in of a tablet or capsule into each tube and placing the disk as a weight, then the determination of the dissolution time of the tablets or capsules is performed by observation of the measurement device and taking of the time of the disintegration time by an operating person.
A disintegration apparatus for test bodies, in particular tablets has become known from the German patent DE 3520034 C1, wherein the test bodies are disposed in containers of the disintegration basket between a Hall generator and a disk furnished with a magnet. The containers of the disintegration basket are heated to a constant temperature with a heating means. When the test body disintegrates, then the disk moves together with the magnet toward the Hall generator, such that the Hall generator delivers a signal, which is led to a registration apparatus after the surpassing of a switching threshold and can be displayed. The transfer of the energy for electrical switching circuits in a disintegration basket is performed through contacts or through a high frequency emitter and high frequency receiver. The transfer of the signals to the registration apparatus is performed by optoelectrical components.
An automatic disintegration time measurement apparatus for the pharmaceutical quality control and production control of tablets and sugar-coated pills within a conducting test liquid is known from the German printed patent document DE 9419245 U1, which disintegration time measurement apparatus comprises a basket like frame disposed in a beaker glass with a plurality of glass tubes disposed in the basket like frame, wherein the floors of the glass tubes are formed by circular sieve plates as stand faces for the glass tubes, wherein each sieve plate comprises two wire grid halves being flown through by current and forming electrodes, wherein the wire grid halves are disposed at a distance and are thereby forming a slot. A test sample is disposed in each glass tube, wherein the test sample is covered by a float, and wherein the float rests on the test sample. The float exhibits on the bottom side an embedded contact frame made of a metallic material. Upon motion of the beaker glass and the disintegration of the tablets, the conductivity of the test fluid changes, wherein the conductivity can be measured between the wire grid halves and the contact frame of the float.
A tablet disintegration time measurement apparatus with moving small tubes in a bath liquid is known from U.S. Pat. No. 3,618,295 having a multitude of electrodes disposed opposite to each other at a distance on the floor of the small tubes containing the tablets. The presence of a tablet interferes with an electromagnetic field applied at the electrodes, wherein the interference influences a time clock, wherein the signals of the time clock can be evaluated.
A device for determining the disintegration time of compressed pharmaceutical mold bodies has become known from the World Intellectual Property Organization publication WO 97/14035, wherein an electric coil is disposed at the floor of the frame around each hole, wherein the electrical coil is part of an electrical oscillating circuit, wherein a conductor loop is disposed on the disk for a path depending damping of the electrical oscillating circuit, wherein the electrical oscillating circuit and the conductor loop are jointly connected to an electrical evaluation device for oscillation generation and evaluation of the measurement results. The coil can be formed as an insertion coil, a single layer coil, or as a multiple layer coil.
Conventional steps for fully automatic measurement started on the one hand always with impermissible changes of the test apparatus, wherein such changes however are permissible only in a very small range according to Deutsches Arzneibuch DAB 10. On the other hand the device according to the last recited document WO 97/14035 delivers relatively precise measurement results, however requires an extensive electronic expenditure in the signal generation and signal evaluation.
It is an object of the present invention to furnish a device of the kind initially recited, which captures contactless the motion of the disks within the device and without larger changes of the pre-scribed parameters for the apparatus according to Deutsches Arzneibuch DAB 10 and which is to determine continuously the decreasing thickness of compressed pharmaceutical mold bodies during the dissolution process.
It is another object of the present invention to furnish a device which reliably and precisely measures a disintegration behavior of a tablet or capsule.
The present invention provides that the central hole of the disk exhibits centeredly a bore starting at the lower cover face of the disk, where a permanent magnet is seated in the bore, wherein the permanent magnet exhibits centeredly a bore hole in the direction of the center axis, wherein the bore hole is aligned with the central bore within the disk, wherein the magnetic field sensor element is disposed in the region of the peripheral edge of the cover face of the permanent magnet in the region of the largest gradient of the magnetic field of the permanent magnet as seen in a top planar view.
Usually the residual thickness of a pharmaceutical mold body is a pre-given set point value. If the actual value of the pharmaceutical mold body is the residual thickness, then the pharmaceutical mold body is deemed to be dissolved.
Advantageously the apparatus is constructed such that the geometry and the thickness of the disks employed as well as the geometry of the test tubes and the construction of the sieve floor of the frame remains unchanged. Similarly the disks and the frames are exchangeable amongst each other, without that a re-calibration of the apparatus has to be performed. In particular such disks can be employed, which exhibit according to the prescription also five holes, wherein one of the five holes is a centered middle hole. The disks are only constructed such that a permanent magnet with a hole is disposed within this disk around the centered middle bore, such that the central bore of the disk is continued by the hole of the permanent magnet. The sleight addition in weight by the permanent magnet can be balanced in a simple way by insertion of small hollow spaces into the disk, such that the pre-scribed weight of the disk is maintained.
Advantageously, the permanent magnet is formed cylindrical and of tubular or sleeve shape, wherein the longitudinal extension of the permanent magnet is larger than the diameter of the permanent magnet. This way the magnetic stray of the permanent magnet can be maintained small. The permanent magnet is completely surrounded of plastic material within the disk, for example a plastic sleeve is inserted into the hole of the permanent magnet.
The magnetic field sensor element can be a Hall generator or a magneto-resistive sensor or a saturable core probe, wherein a Hall generator is preferred, where the Hall generator is capable of measuring even smallest changes in field strength.
The magnetic field sensor element or, respectively, the Hall generator is disposed in the region of the largest gradient of the magnetic field, as soon as the permanent magnet stands directly opposed to the magnetic field sensor element in the final position of the disk. For this reason it is advantageous that the main part of the sensor with small dimensions is disposed so far spaced apart that the main part of the sensor with small dimensions is disposed immediately below the annular front face of the magnet, that is in a top planar view sideways to the hole of the permanent magnet.
Furthermore each channel is measured several times during a disintegration process with the apparatus and an average value formed from the measurements. It is also possible to scan each of the six magnetic field sensor elements by way of a fast multiplexer.
The novel features which are considered as characteristic for the invention are set forth in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.